BT4600 does not work

I was attempting to set up the new phone today, and was adding contacts, but it somehow got to a screen stating exit without saving? It then stated yes or no - (press the left button for yes and the right button for no). Unfortunately, whatever button I press, I can't get out of this screen - the phone has completely locked. I cannot turn the phone off by pressing and holding down the red phone button either. If anyone has any suggestions, I would be very grateful.

Sorry, have resolved this myself by taking the batteries out of the handset and reinserting them. As you can see, I was panicking a bit.